The present invention is generally related to a concrete or composite concrete beam with an external reinforcement system, in order to improve the response of the beam to external forces, reduce the weight of the beam, and eliminated crack formation in the concrete.
Known methods of constructing a reinforced beam, have as their objective the improvement of the response of the beam to the external forces, hence the capacity of the beam. There are two main methods of constructing a reinforced beam. According to the first alternative method, the capacity of the beam is improved by means of an internal reinforcement sytsem. In this method the beam is made of an anisotropic material, concrete for instance, to take compression, and it is reinforced with an internal reinforcement, steel for instance, to take tension.
According to the second alternative method, the capacity of the beam is improved by introducing an internal stress in the beam, of such magnitude and distribution, to counteract the expected forces. In this method the beam can be made of any material, concrete, steel or fiberglass for instance, and the internal stresses are created by means of bars or wires, made of steel or fiberglass for instance, with a higher strength.
One disadvantage of the first method is that under the external forces, the said anisotropic material, concrete for instance, exhibits cracks under the external loads in the tension area of the beam, exposing the said internal reinforcement, steel for instance, to corrosion. A further disadvantage of the former method is that the weight of the beam is too great and the portion of the beam that is cracked does not participate to take loads, being a ballast of the beam.
The major disadvantage of the second method is that the amount of the initial stress is limited by the capacity of the beam at transfer of the force from the said bars or wires to the beam.